Wilson was hit by debris from the car of rookie Sage Karam, who was leading the ABC Supply 500 when his No. 8 Chip Ganassi Racing Chevrolet spun on its own in Turn 1 on Lap 179 of the 200-lap race Sunday.

The IndyCar community was rocked in 2011 when two-time Indianapolis 500 winner Dan Wheldon died of blunt force trauma when his head struck a post in a catchfence during an IndyCar race at Las Vegas Motor Speedway’s 1.5-mile oval. The 2005 IndyCar champion, 33, was beloved on the series.

Seven-time NASCAR Cup champion Dale Earnhardt Sr. died Feb. 18, 2001, of a basilar skull fracture when his car slammed into the Turn 4 wall at Daytona International Speedway on the final lap of the Daytona 500. Earnhardt earned the nickname ”Intimidator” for his racing style and his fan base remains strong today, more than 14 years after his death at 49.

Wilson’s death now will raise questions again of whether it is time for IndyCar to enclose its cockpits.

Minutes after Wilson was struck on the helmet by what appeared to be the nose cone of Karam’s car during the late stages of Sunday’s Verizon IndyCar Series ABC Supply 500 at Pocono Raceway, Ryan Hunter-Reay addressed the subject in a subdued winner’s press conference.

“These cars are inherently dangerous with the open cockpit like that, head exposed,” Hunter-Reay said. “Maybe in the future we can work toward some type of (canopy). We’ve seen some concept renderings of something that resemble a canopy — not a full jet fighter canopy, but something that can give us a little protection but keep the tradition of the sport.”

Canopies — plastic enclosures over open cockpits — have been proposed before, most recently after a Formula 1 crash in October 2014 that left Jules Bianchi in a coma for nine months — he died in July — and after a piece of debris struck James Hinchcliffe’s helmet during the Indianapolis Grand Prix in May 2014. Hinchcliffe suffered a concussion and later said he couldn’t remember anything about the accident.

Wheldon’s death put spotlight on catchfence safety

Wheldon died Oct. 16, 2011, just five months after winning his second Indianapolis 500.

He was killed when his Dallara-Honda sailed 325 feet through the air in a fiery 15-car wreck that caused the race’s cancellation.

Wheldon’s death prompted a firestorm of controversy for IndyCar and then-CEO Randy Bernard, who had offered a $5 million bounty in the season finale to attract moonlighting NASCAR drivers (Wheldon was appointed the sole eligible driver for the prize when there were no takers).

It also raised many questions about the safety of the chassis, which was in its last race of an eight-year run. The 2012 model, which was tested by Wheldon and named for him (“DW12”), featured new safety enhancements. The tub was designed to provide more protection against debris entering the cockpit, which was made wider to aid in driver extraction. Energy-absorbing seat insets added padding beneath and behind the driver.

Perhaps most notably, a wider underwing and rear “bumper covers” were intended to reduce the risk of cars going airborne by touching wheels. In an interview in 2012 with USA TODAY Sports, four-time champion Dario Franchitti — who retired from the sport after a crash at a temporary street course in Houston sent his car sailing into temporary fencing and left him with a concussion and broken back and ankle — said “the series has tried hard to do stuff with the new car, but I’m not sure they’ve made the progress.”

Franchitti also is one of several drivers who have complained about the fence configuration at Vegas, which places its poles on the outside of the catchfence (unlike some tracks that wrap the poles inside the fencing).

To reduce speeds in the interest of safer racing, IndyCar also could consider restricting horsepower or adding “drag” to increase aerodynamic resistance.

Catchfences also were in the spotlight after a Nationwide Series crash at Daytona in February 2013. Kyle Larson’s car went airborne on the final lap, its engine went through a fence and debris, including a tire, scattered among the crowd, injuring two dozen fans.

Hunter-Reay, the 2012 IndyCar champion, told USA TODAY Sports at the time: “The fence acts as a cheese grater, and the car is the cheese. When it gets airborne, the fence tears it up into pieces. It’s an industry-wide problem, and one we can fix quickly. It would be revolutionary for the sport, and it’s at the forefront of what we’ve been talking about for five years. … The problem is that the cost would be front-loaded. It would be extremely expensive.”

Again in July at Daytona, Austin Dillon’s car went into the catchfence after the start/finish line on the final lap of the Coke Zero 400 Sprint Cup race. Dillon was uninjured. His engine block separated from his car and flames leapt from it as it came to rest on the apron. Dillon was hit a second time, by Brad Keselowski, who tried to slow through the melee but lost control and clipped the No. 3 Chevrolet again. Five fans were injured. One was transported to a local hospital, treated and released. The other four were treated at the infield care center.

Deadly crashes have robbed stock car racing of some of its leading drivers, including Earnhardt Sr., Fireball Roberts, Joe Weatherly, Neil Bonnett and Tiny Lund. The sport also has lost some of its promising young drivers such as Adam Petty and Kenny Irwin Jr. Bad on-track accidents also have shortened the careers of numerous drivers, including prominent names such as Bobby Allison, Lee Petty and Ernie Irvan.

Some of NASCAR’s most significant safety advances have followed major accidents. And some changes, especially reinforcement and expansion of trackside fencing, have been made after accidents sent pieces of cars flying into grandstands.

Roberts’ death as a result of a fiery crash at Charlotte Motor Speedway in 1964 led to the development of sturdier fuel cells. Cars going airborne at racing’s fastest tracks led to roof flaps, which are designed to slow spinning cars and lessen the chances of flight. Hard impact with concrete walls – a factor in the deaths of Earnhardt, Bonnett, Adam Petty and Irwin, among many others – led to the development of so-called “soft walls,” in effect adding a layer of padding in front of concrete walls and barriers.

Earnhardt’s death on the final lap of the 2001 Daytona 500 was a watershed moment in NASCAR history.

Dale Earnhardt in 1996. (Tom Strattman, AP)

The loss of one of the sport’s icons – a seven-time Cup champion and one of auto racing’s most popular figures whose moniker was ‘The Intimidator’ for his aggressive style – resulted in an extensive investigation by NASCAR officials and experts outside the sport, leading to such developments as soft walls and head and neck restraints (HANS devices) worn by drivers.

SAFER (Steel and Foam Energy Reduction) barriers were used for the first time at Indianapolis Motor Speedway in 2002. The technology became mandatory at all NASCAR-sanctioned tracks within a few years and is credited with saving lives and preventing serious injuries in accidents in which out-of-control cars have hit walls with violent force.

There has not been a death in NASCAR’s major series since Earnhardt’s fatal accident.

The stock car was tweaked to offer drivers more protection during racing. New safety features included: larger roof flaps, the addition of a forward roof bar and center support bar for added support during a rollover; stronger windshields to prevent debris from breaking through and a larger window net.

IndyCar now could face more questions about whether the drivers can be further protected.

In the wake of Earnhardt’s death, NASCAR spent $10 million constructing an R&D Center in Concord, N.C. Completed in early 2003, the R&D Center’s initial primary focus was enhancing safety to avoid the loss of another superstar.

Earnhardt was the fourth driver to die in a NASCAR-sanctioned event in the span of 10 months.

–Petty, grandson of NASCAR legend and seven-time champion Richard Petty and son of then-driver and current TV analyst Kyle Petty, died after a crash in the then-Busch Series practice at New Hampshire Motor Speedway on May 12, 2000.

–Irwin Jr. died two months later, on July 7, 2000, after crashing during a practice session for a Cup race, also at New Hampshire Motor Speedway.

–And Tony Roper died Oct. 13, 2000, during a Truck Series race at Texas Motor Speedway. His truck veered hard right into the outside track wall during an accident at the 1.5-mile speedway.

The “Car of Tomorrow” made its debut six years later. Drivers hated its boxy and generic aesthetics, but it offered more safety features.

Earnhardt’s death also triggered drivers being required to wear the HANS device (which is designed to prevent the basilar skull fractures that killed Earnhardt, Petty, Irwin and Roper).